Divergent Isomerization Behavior and Rhodium(I) Coordination Chemistry of Indenyl Ligands Bearing either One or Two Pnictogen Donor Fragments

Article abstract of DOI:10.1021/om0340589

1-(Diphenylphosphino)-2-(dimethylamino)indene (2c) has been prepared in 61% yield and upon exposure to Al₂O₃ is mostly isomerized to 3-(diphenylphosphino)-2-(dimethylamino)-indene (2d) (2c:2d ≈ 1:3); similarly, 1-(diisopropylphosphino)-2-(dimethylamino)indene (2a) is only partially converted to the corresponding C3 isomer (2b) upon treatment with Al₂O₃ (2a:2b ≈ 3:1). In contrast, 1-(diisopropylphosphino)indene (6a) has been prepared in 92% yield and is easily converted to 3-(diisopropylphosphino)indene (6b) on passing over Al ₂O₃; 0.5 equiv of [(η⁴-COD)RhCl] ₂ and 6b combine to give [(K¹-P-6b)(η ⁴-COD)RhCl] (7) in 79% yield. Treatment of either 2-(dimethylamino)indene (1) or 6b with a stoichiometric amount of n-BuLi, followed by the addition of 0.5 equiv of [(η ⁴-COD)RhCl] ₂, produces the (η⁵-indenyl)-rhodium(I) complexes 8 (53% yield) and 9 (88% yield), respectively, in which the pnictogen donor is apparently not coordinated to the rhodium center. When 2.5 equiv of n-BuLi is combined with 6b and subsequently treated with 0.5 equiv of [(η ⁴-COD)RhCl]₂, 9 is also produced, along with a small amount of the unusual Rh₂Li₂ species 10. The crystallographically determined structures of 2d, 3·C₆H ₆, 7, and 10·C₇H₈ are reported.

Full text of DOI:10.1021/om0340589

Organometallics 2003, 22, 5185-5192
5185
Articles
Diver gen t Isom er iza tion Beh a vior a n d Rh od iu m (I)
Coor d in a tion Ch em istr y of In d en yl Liga n d s Bea r in g
eith er On e or Tw o P n ictogen Don or F r a gm en ts
J udy Cipot, Dominik Wechsler, and Mark Stradiotto*
Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J 3
Robert McDonald and Michael J . Ferguson
X-ray Crystallography Laboratory, Department of Chemistry, University of Alberta,
Edmonton, Alberta, Canada T6G 2G2
Received J uly 21, 2003
1-(Diphenylphosphino)-2-(dimethylamino)indene (2c) has been prepared in 61% yield and
upon exposure to Al2O3 is mostly isomerized to 3-(diphenylphosphino)-2-(dimethylamino)-
indene (2d ) (2c:2d ≈ 1:3); similarly, 1-(diisopropylphosphino)-2-(dimethylamino)indene (2a )
is only partially converted to the corresponding C3 isomer (2b) upon treatment with Al2O3
(2a :2b ≈ 3:1). In contrast, 1-(diisopropylphosphino)indene (6a ) has been prepared in 92%
yield and is easily converted to 3-(diisopropylphosphino)indene (6b) on passing over Al2O3;
0.5 equiv of [(η4-COD)RhCl]2 and 6b combine to give [(κ1-P-6b)(η4-COD)RhCl] (7) in 79%
yield. Treatment of either 2-(dimethylamino)indene (1) or 6b with a stoichiometric amount
of n-BuLi, followed by the addition of 0.5 equiv of [(η4-COD)RhCl]2, produces the (η5-indenyl)-
rhodium(I) complexes 8 (53% yield) and 9 (88% yield), respectively, in which the pnictogen
donor is apparently not coordinated to the rhodium center. When 2.5 equiv of n-BuLi is
combined with 6b and subsequently treated with 0.5 equiv of [(η4-COD)RhCl]2, 9 is also
produced, along with a small amount of the unusual Rh2Li2 species 10. The crystallographi-
cally determined structures of 2d , 3‚C6H6, 7, and 10‚C7H8 are reported.
In tr od u ction
dehydrogenative coupling of triethylsilane and styrene.4
During the course of this study we observed that (a) the
clean conversion of 3 into 4 is accompanied by a
structural rearrangement of the indene ligand in which
Transition-metal complexes supported by π-coordi-
nated η5-indenyl ligands have a longstanding history in
the field of organometallic chemistry and continue to
figure importantly in current research.1 In particular,
main-group-functionalized indenyl ligands have at-
tracted considerable attention,2 since they have been
shown to impart interesting reactivity properties to both
early- and late-transition-metal fragments.3 Recently we
reported the synthesis of the P,N-functionalized indene
2a and demonstrated that this versatile ligand system
can be used in the preparation of neutral (3), cationic
(4), and zwitterionic (5) Rh(I) complexes (Scheme 1);
compounds 4 and 5 have been shown to catalyze the
i
the formerly allylic (C1) Pr2P substituent is placed at
the vinylic (C3) position and (b) in stark contrast to the
numerous (η4-COD)Rh(η5-indenyl) (COD ) 1,5-cyclooc-
tadiene) complexes,5 the [(η4-COD)Rh]+ fragment in 5
selectively binds in a κ2-P,N fashion to the periphery of
the carbanion generated upon deprotonation of 2a ,
rather than coordinating in the usual η5 manner to the
face of the carbocyclic framework. In light of these
observations, we became interested in preparing directly
the ligand 2b (i.e. the C3 isomer of 2a ) and in gaining
a better understanding of the factors that favor the
unusual κ2 bonding arrangement found in 5. Herein we
* To whom correspondence should be addressed. E-mail:
mark.stradiotto@dal.ca.
(1) (a) Calhorda, M. J .; Veiros, L. F. Coord. Chem. Rev. 1999, 185-
186, 37. (b) Lobanova, I. A.; Zdanovich, V. I. Russ. Chem. Rev. (Engl.
Transl.) 1988, 57, 967.
(4) Stradiotto, M.; Cipot, J .; McDonald, R. J . Am. Chem. Soc. 2003,
125, 5618.
(5) For some recently reported Rh(η5-indenyl) complexes, see: (a)
Santi, S.; Ceccon, A.; Carli, F.; Crociani, L.; Bisello, A.; Tiso, M.; Venzo,
A. Organometallics 2002, 21, 2679. (b) Santi, S.; Ceccon, A.; Crociani,
L.; Gambaro, A.; Ganis, P.; Tiso, M.; Venzo, A.; Bacchi, A. Organome-
tallics 2002, 21, 565. (c) Schumann, H.; Stenzel, O.; Dechert, S.;
Girgsdies, F.; Blum, J .; Gelman, D.; Halterman, R. L. Eur. J . Inorg.
Chem. 2002, 211. (d) Rupert, K. C.; Liu, C. C.; Nguyen, T. T.; Whitener,
M. A.; Sowa, J . R., J r. Organometallics 2002, 21, 144. (e) Westcott, S.
A.; Kakkar, A. K.; Taylor, N. J .; Roe, D. C.; Marder, T. B. Can. J . Chem.
1999, 77, 205.
(2) Stradiotto, M.; McGlinchey, M. J . Coord. Chem. Rev. 2001, 219-
221, 311.
(3) For some recent examples, see: (a) Xie, Z. Acc. Chem. Res. 2003,
36, 1. (b) Fan, W.; Waymouth, R. M. Macromolecules 2003, 36, 3010.
(c) Lee, M. H.; Han, Y.; Kim, D.; Hwang, J .-W.; Do, Y. Organometallics
2003, 22, 2790. (d) Kamigaito, M.; Watanabe, Y.; Ando, T.; Sawamoto,
M. J . Am. Chem. Soc. 2002, 124, 9994. (e) Greidanus, G.; McDonald,
R.; Stryker, J . M. Organometallics 2001, 20, 2492.
10.1021/om0340589 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/18/2003

5186 Organometallics, Vol. 22, No. 25, 2003
Cipot et al.
Sch em e 1. Syn th esis of th e P ,N-Su bstitu ted
In d en e Liga n d 2a a n d Rela ted Rh (I) Der iva tives,
In clu d in g th e Zw itter ion ic Com p lex 5
F igu r e 1. Crystallographically determined structure of 3‚
C6H6, shown with 40% displacement ellipsoids. Selected
hydrogen atoms and the benzene solvate have been omitted
for clarity. Selected interatomic distances (Å): Rh-Cl,
2.3774(5); Rh-P, 2.3427(5); Rh-C11, 2.137(2); Rh-C12,
2.115(2); Rh-C15, 2.232(2); Rh-C16, 2.190(2); P-C1,
1.882(2); N-C2, 1.390(3); C1-C2, 1.530(3); C2-C3, 1.351(3).
Selected interatomic angles (deg): C2-N-C27, 118.0(2);
C2-N-C28, 116.2(2); C27-N-C28, 112.3(2).
The ligand 2a does not undergo such a structural
rearrangement upon coordination to rhodium,4 as con-
firmed by the crystallographically determined structure
of [(κ1-P,N-2a )(η4-COD)RhCl]‚C6H6 (3‚C6H6; Figure 1).8
Selected data for all of the crystallographically charac-
terized compounds reported herein are collected in Table
1. The rhodium center in 3‚C6H6 possesses a square-
planar geometry commonly observed for Rh(I) (d8)
complexes; as expected, the metrical parameters indi-
cate that the alkene donor (C11, C12) trans to chloride
binds more tightly to the metal center than the corre-
sponding alkene (C15, C16) trans to phosphine. At-
tempts to promote the C1 to C3 isomerization of the
indenyl fragment in 3, either by stirring over alumina
or by heating, resulted in decomposition.
In an effort to determine the possible role of the
isopropyl substituents on phosphorus in blocking the
isomerization of 2a to 2b, the related 1-diphenylphos-
phino-substituted aminoindene 2c was prepared and its
isomerization behavior examined (Scheme 2). Similar
to what was observed for 2a , a C6D6 solution of pure 2c
was transformed into a mixture of 2c and 2d (∼1:3)
after exposure to alumina for several hours. Also similar
to the 2a /2b system, attempts to drive this rearrange-
ment process by heating a 2c/2d mixture at 80 °C in
toluene were unsuccessful, leading to the formation of
numerous phosphorus-containing products.
Although we were unable to efficiently separate 2c
from 2d , the predominant formation of the latter species
in the aforementioned isomerization experiment allowed
for 1H and 31P NMR resonances attributable to 2d to
be assigned. Moreover, in one instance we were able to
crystallize minute quantities of 2d that proved to be
suitable for single-crystal X-ray diffraction analysis. The
crystallographically determined structure of 2d is pre-
sented in Figure 2 and by analogy provides indirect
evidence for 2b. The overall geometric features in 2d
are comparable to those of 3-(diphenylphosphino)in-
report on our pursuit of these targets, including the
crystallographic identification of a new “non-η5” struc-
tural motif for rhodium-indenide complexes.
Resu lts a n d Discu ssion
The conversion of 2a into 2b (eq 1) was attempted
using the method of Anderson and co-workers,6 who
reported that while the isomerization of 1-(diphenylphos-
phino)indene into 3-(diphenylphosphino)indene occurs
slowly on standing in solution, this transformation
proceeds rapidly and quantitatively upon exposure to
alumina.7 After stirring a C6D6 solution of pure 2a over
alumina for several hours, 31P NMR signals attributable
to 2a (19.6 ppm) and what we presume to be the vinylic
isomer (vide infra) 2b (-2.9 ppm) were observed.
Although this transformation appeared to proceed with-
out the formation of byproducts, complete conversion
could not be achieved; even after several days the ratio
of 2a to 2b was found only to be ∼3:1. Efforts to promote
this isomerization process by heating a toluene solution
of 2a at 80 °C were also unsuccessful, generating a
mixture of 2a , 2b, and other phosphorus-containing
products.
Anderson and co-workers also observed that the C1
to C3 isomerization of (diphenylphosphino)indene occurs
when the phosphorus center is coordinated to platinum.6
(7) Stradiotto, M.; Kozak, C.; McGlinchey, M. J . J . Organomet.
Chem. 1998, 564, 101.
(8) Although not isomorphous, the molecular geometry and metrical
parameters of 3 found in 3‚C6H6 are quite similar to those found in
3‚CH2Cl2.4
(6) Fallis, K. A.; Anderson, G. K.; Rath, N. P. Organometallics 1992,
11, 885.

Rh(I) Chemistry of Donor-Functionalized Indenes
Organometallics, Vol. 22, No. 25, 2003 5187
Ta ble 1. Cr ysta l Da ta for 2d , 3‚C6H6, 7, a n d 10‚C7H8
2d
23H22NP
343.39
0.34 × 0.14 × 0.08
monoclinic
P21/c
12.518 (1)
8.2259 (8)
18.445 (2)
90
102.876 (2)
90
1851.5 (3)
4
1.232
0.153
52.82
-15 e h e 14
-10 e k e 9
-22 e l e 22
9517
3792
0.0475
3‚C6H6
7
10‚C7H8
empirical formula
formula wt
cryst dimens
cryst syst
space group
a (Å)
C
C31H44ClNPRh
600.00
0.31 × 0.30 × 0.16
monoclinic
P21/n
14.765 (1)
7.9199 (6)
25.158 (2)
90
105.251 (1)
90
C23H33ClPRh
478.82
0.39 × 0.24 × 0.09
C53H70Li2P2Rh2
988.73
0.34 × 0.22 × 0.20
monoclinic
I2/a
18.857 (1)
17.4958 (9)
14.0506 (7)
90
97.527 (1)
90
triclinic
P1h
7.7514 (5)
10.6743 (7)
14.4876 (9)
75.040 (1)
75.390 (1)
70.382 (1)
1072.7 (1)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
2838.2 (4)
4
4595.7 (4)
4
Z
Fcalcd (g cm-3
)
1.404
0.773
52.78
1.482
1.000
52.76
1.429
0.823
52.74
µ (mm-1
)
2θ limit (deg)
index ranges
-17 e h e 18
-9 e k e 9
-31 e l e 29
16 608
-9 e h e 9
-13 e k e 13
-18 e l e 18
6585
-22 e h e 23
-21 e k e 21
-17 e l e 11
11 299
total no. of data collected
no. of indep rflns
Rint
5786
0.0232
4334
0.0175
4681
0.0230
abs cor
empirical (SADABS)
0.9879-0.9498
3792/0/228
0.0491
0.1260
1.016
empirical (SADABS)
0.8864-0.6100
5786/0/316
0.0259
0.0690
1.031
face indexed
0.9154-0.6964
4334/0/235
0.0254
0.0658
1.046
empirical (SADABS)
0.8527-0.7672
4681/0/269
0.0320
0.0885
1.050
range of transmissn
no. of data/restraints/params
2
R1 (Fo g 2σ(Fo2))
wR2 (Fo g -3σ( Fo2))
2
goodness of fit
that the lone pair of electrons on nitrogen in 2d is in
conjugation with the indene π-system. This bonding
scenario provides a possible rationale as to why the
isomerization of 2a /2b or 2c/2d over alumina is slug-
gish, whereas the transformation of 1-(diphenylphos-
phino)indene6 or 1-(diisopropylphosphino)indene (6a ,
vide infra) into the corresponding C3 isomer is rapid.
In consideration of steric factors alone, it may be that
the large R2P fragment is best accommodated at the
allylic (C1) position in either 2a or 2c, when the
dimethylamino group adopts a coplanar geometry with
the indene ring. Furthermore, conjugation of the lone
pair on nitrogen should greatly increase the electron
density of the indene ring in either 2a or 2c and, in
doing so, should reduce the acidity of the benzylic
hydrogen atom at the C1 position.10 Since the C1 to C3
isomerization of phosphinoindenes over alumina can be
viewed as a deprotonation/reprotonation sequence,6,7 the
increased pKa of the benzylic proton on going from
1-(diphenylphosphino)indene to either 2a or 2c should
be manifested in an increased barrier to isomerization.
This phenomenon may also have relevance to the rapid
C1 to C3 isomerization of the coordinated indene ligand
on going from 3 to 4 (Scheme 1). As in 2d , the short
N-C2 distance in 3‚C6H6 (1.390(3) Å) suggests that the
lone pair of electrons on the uncoordinated dimethyl-
amino group is conjugated with the indene ring, possibly
inhibiting the C1 to C3 rearrangement of the bound
ligand (2a ) in 3.11 Coordination of the nitrogen donor
to rhodium following abstraction of the chloride ligand
in 3 would disrupt this conjugation, enabling the
isomerization of 2a to 2b to proceed within the metal
F igu r e 2. Crystallographically determined structure of
2d , shown with 40% displacement ellipsoids. Selected
interatomic distances (Å): P-C3, 1.807(2); N-C2, 1.352(3);
C1-C2, 1.518(3); C2-C3, 1.380(3). Selected interatomic
and torsion angles (deg): C2-N-C8, 121.6(2); C2-N-C9,
122.8(2); C8-N-C9, 115.5(2); C1-C2-N-C8, 5.2(3); C3-
C2-N-C9, -0.1(4).
Sch em e 2. Syn th esis a n d Attem p ted
Isom er iza tion of Com p ou n d s 2c a n d 2d
dene.6 In addition, the coplanarity of the non-hydrogen
atoms (excluding the phenyl substituents on phospho-
rus)9 and the short N-C2 distance (1.352(3) Å) indicate
(10) Whereas the pKa value of the benzylic protons on indene itself
is 20.1, the incorporation of a 2-(cyclo-C4H8N) substituent causes the
pKa of the benzylic protons to rise to 24.5; see: Bordwell, F. G.; Satish,
A. V. J . Am. Chem. Soc. 1992, 114, 10173.
(9) The mean deviation from the plane defined by C1, C2, C3, C3a,
C4, C5, C6, C7, C7a, C8, C9, N, and P in 2d is less than 0.05 Å. Within
error, the sum of the angles around N in 2d is 360°.
(11) By comparison, the N-C2 and Rh-P distances in 4 are 1.459(6)
and 2.305(1) Å, respectively: Cipot, J .; Abeysekera, D.; Ferguson, M.
J .; McDonald, R.; Stradiotto, M. Unpublished results.

5188 Organometallics, Vol. 22, No. 25, 2003
Cipot et al.
Sch em e 4. Gen er a tion of th e Mon on u clea r η5
Com p lex 9 a n d th e Rh 2Li2 Sp ecies 10
F igu r e 3. Crystallographically determined structure of 7,
shown with 40% displacement ellipsoids. Selected hydrogen
atoms have been omitted for clarity. Selected interatomic
distances (Å): Rh-Cl, 2.3589(6); Rh-P, 2.3366(5); Rh-
C11, 2.136(2); Rh-C12, 2.124(2); Rh-C15, 2.211(2); Rh-
C16, 2.199(2); P-C3, 1.821(2); C1-C2, 1.500(3); C2-C3,
1.344(3).
0.5 equiv of [(η4-COD)RhCl]2 produced the anticipated
η5-indenyl complex, 8, in 53% yield (eq 2). Similarly,
Sch em e 3. Isom er iza tion of 6a to 6b, F ollow ed by
Com p lexa tion w ith Rh od iu m , P r od u cin g 7
treatment of 6b with 1 equiv of n-BuLi proceeded
cleanly in diethyl ether; in situ monitoring of the
reaction (31P NMR) confirmed the consumption of 6b,
accompanied by the appearance of one new phosphorus-
containing product (6-Li) at -8.9 ppm. Addition of 0.5
equiv of [(η4-COD)RhCl]2 to the reaction mixture pro-
duced the η5 species 9 as the only phosphorus-containing
product (δ(31P) -11.9), which in turn was isolated in
88% yield (Scheme 4). The lack of rhodium coupling to
phosphorus is in keeping with the structural formula-
tion proposed for 9. These preliminary experiments
confirm that the ability of the adjacent phosphorus and
nitrogen donors to chelate the Rh(I) center in 5 is critical
in order to circumvent η5 coordination.
In the pursuit of 9, a reaction was inadvertently
carried out in which 6b was initially treated with excess
(2.5 equiv) rather than a stoichiometric quantity of
n-BuLi. Despite the excess base employed, the clean
formation of 6-Li was noted (31P NMR) and subse-
quently [(η4-COD)RhCl]2 (0.5 equiv) was added to the
reaction mixture. After approximately 2 h, the consump-
tion of 6-Li along with the formation of 9 as the major
product was observed (31P NMR); the mixture was then
filtered and set to crystallize at -30 °C. Although no
crystalline material was obtained from this reaction
mixture initially, storage for an extended period of time
at reduced temperatures ultimately produced a few
X-ray-quality crystals. Surprisingly, single-crystal X-ray
diffraction analysis revealed that this material was not
the anticipated η5-indenyl complex 9 but rather the
unusual dimeric Rh2Li2 species 10 (Scheme 4). Reex-
amination of the resulting supernatant solution by using
31P NMR techniques revealed the previously observed
singlet at -11.9 ppm attributable to 9, along with a
number of other rhodium-coupled signals between 49
coordination sphere and leading to the exclusive forma-
tion of [(κ2-P,N-2b)(η4-COD)Rh]+BF4 (4).12
-
In keeping with the aforementioned arguments, sub-
stitution of the 2-dimethylamino fragment in 2a for a
hydrogen atom facilitates the C1 to C3 isomerization
process. 1-(Diisopropylphosphino)indene (6a ) was pre-
pared in 92% yield and in turn was cleanly converted
to 3-(diisopropylphosphino)indene (6b) upon exposure
to alumina (Scheme 3). Treatment of 6b with 0.5 equiv
of [(η4-COD)RhCl]2 generated the expected coordination
complex [(κ1-P-6b)(η4-COD)RhCl] (7) in 79% yield. The
crystallographically determined structure of 7 is pre-
sented in Figure 3 and confirms the presence of the
coordinated ligand 6b. From the perspective of the
rhodium coordination sphere, the structural attributes
of 7 mirror those of 3‚C6H6 and therefore do not warrant
further discussion.
In addition to examining the isomerization behavior
of 2a and related derivatives, studies were conducted
in an effort to identify the substitution pattern needed
in order to promote the peripheral (rather than facial)
binding of indenide ligands to rhodium(I) fragments, as
occurs in the unprecedented [κ2-P,N]Rh(I) zwitterion 5
(Scheme 1).4 Our initial approach was to examine the
impact of systematically removing either the diisopro-
pylphosphino or dimethylamino substituents from the
precursor, 2a . Lithiation of 1 followed by treatment with
(12) The related isomerization of phospholes to phospholenes within
the coordination sphere of Pd(II) has recently been reported: Leca,
F.; Sauthier, M.; le Guennic, B.; Lescop, C.; Toupet, L.; Halet, J .-F.;
Re´au, R. Chem. Commun. 2003, 1774.

Rh(I) Chemistry of Donor-Functionalized Indenes
Organometallics, Vol. 22, No. 25, 2003 5189
Sch em e 5. Tw o P ossible Mech a n istic Rou tes to 10
F igu r e 4. Crystallographically determined structure of 10‚
C7H8, shown with 40% displacement ellipsoids. Selected
hydrogen atoms and the toluene solvate have been omitted
for clarity. Selected interatomic distances (Å): Rh-P,
2.3536(6); Rh-C7, 2.093(3); Rh-C11, 2.161(3); Rh-C12,
2.198(3); Rh-C15, 2.198(3); Rh-C16, 2.233(3); P-C1,
1.765(3); Li-C1, 2.264(5); Li-C2, 2.257(5); Li-C3, 2.267(5);
Li-C3a, 2.306(5); Li-C7a, 2.293(5); Li-C7B*, 2.193(5);
C1-C2, 1.422(4); C2-C3, 1.388(4); C3-C3a, 1.420(4);
C3a-C4, 1.420(4); C4-C5, 1.364(5); C5-C6, 1.414(4); C6-
C7, 1.400(4); C7-C7a, 1.424(4); C7a-C1, 1.428(4) (*C7B
is the position related to C7 via the crystallographic
inversion center).
leading to (η4-COD)Rh(n-Bu) upon loss of LiCl; a
sequence of â-hydride elimination, C-H oxidative ad-
dition, and H2 reductive elimination steps could then
produce 11.13 Coordination of rhodium to the phosphine
unit of 6-Li, as in 12, followed by insertion into the
C7-H bond would generate the Rh(III) intermediate 13.
Reductive elimination of 2-butene, followed by dimer-
ization, then generates 10. An alternative mechanistic
pathway (B) has [(η4-COD)RhCl]2 reacting directly with
6-Li at the C7 position, producing 14. Subsequent
rearrangement to 15 reestablishes the aromaticity of the
C6 ring, and reaction with the excess n-BuLi present,
followed by dimerization, produces 10.
and 75 ppm. Efforts to isolate more of 10 from this
reaction mixture were in vain. Moreover, all attempts
to rationally prepare 10, either by using the synthetic
methodology presented above or via the addition of 1.0
equiv of 6-Li to a preformed mixture of 0.5 equiv of [(η4-
COD)RhCl]2 and 1.0 equiv of n-BuLi (see Scheme 5,
path A) were unsuccessful, and so we are presently
unable to provide any spectroscopic characterization
data for this highly unusual rhodium-indenide com-
plex.
Con clu sion s
The structure of 10‚C7H8 is presented in Figure 4 and
is comprised of a dimeric pair of rhodium-substituted
lithium indenide fragments that are related by a crys-
tallographically imposed center of inversion. Each of the
[(η4-COD)Rh] fragments in 10 is coordinated both to a
pendant phosphine donor and to the C7 position within
a single indenide ring. In turn, the lithium atoms serve
to bridge the halves of 10, bonding to the C5 unit of one
indenide fragment and to the C7 carbon of the adjacent
indenide unit. The Rh-P distance in 10 (2.3536(6) Å)
is comparable to those found in the related phosphino-
indene complexes 3, 4, and 7.4,11 In contrast, the P-C1
bond in 10 (1.765(3) Å) is contracted significantly
relative to the related distances in 3, 4, and 74,11 and is
best compared to the P-Cindenide bond in the zwitterionic
complex 5 (1.758(2) Å).4
In an attempt to rationalize the formation of 10, we
tentatively propose two simplified mechanistic path-
ways (A and B), which are outlined in Scheme 5; other
equally viable routes to 10 could also be envisioned. One
of the proposed mechanistic pathways (A) begins with
the reaction of [(η4-COD)RhCl]2 with the excess n-BuLi
remaining after the formation of 6-Li, presumably
From the experimental data presented in this report,
it is evident that the isomerization behavior of indenes
bearing only one group 15 donor can differ significantly
from indenes containing two adjacent group 15 substit-
uents; whereas 1-(diisopropylphosphino)indene is easily
transformed into 3-(diisopropylphosphino)indene, the
introduction of a 2-dimethylamino substituent greatly
inhibits this rearrangement process. The synthetic work
reported herein also demonstrates that while a lithiated
indene bearing adjacent diisopropylphosphino and di-
methylamino substituents has been shown to form an
unusual zwitterionic κ2-P,N-indenide complex of rhod-
ium(I),4 removal of either of these group 15 fragments
results in the formation of the corresponding pnictogen-
substituted (η5-indenyl)rhodium(I) species, in which the
pendant group 15 donor is apparently not involved in
bonding to rhodium. With this key design feature in
mind, we are currently examining a series of bidentate
ligand precursors structurally related to 2a that incor-
(13) The formation of 11 has been reported: (a) Fryzuk, M. D. Inorg.
Chem. 1982, 21, 2134. (b) Stuehler, H. O.; Mueller, J . Chem. Ber. 1979,
122, 1359.

5190 Organometallics, Vol. 22, No. 25, 2003
Cipot et al.
generated a pale yellow solution, which was transferred away
from the remaining insoluble materials via cannula filtration.
Removal of the toluene and any other volatile materials in
vacuo yielded 2c (0.86 g, 2.52 mmol, 61%). Anal. Calcd for
C23H22NP: C, 80.44; H, 6.46; N, 4.08. Found: C, 80.51; H, 6.60;
N, 3.99. 1H NMR (C6D6): δ 7.42-7.37 (m, 2H, Ar-H’s), 7.22-
6.92 (m, 10H, Ar-H’s), 6.71-6.69 (m, 2H, Ar-H’s), 5.13 (s,
porate a diversity of p-block donors. Reports pertaining
to the use of these in the preparation of neutral, cationic,
and zwitterionic transition-metal complexes are forth-
coming.
Exp er im en ta l Section
2
1H, C3-H), 4.26 (d, J PH ) 5.2 Hz, 1H, C1-H), 2.56 (s, 6H,
Gen er a l Con sid er a tion s. All manipulations were con-
ducted in the absence of oxygen and water under an atmo-
sphere of dinitrogen, either by using standard Schlenk meth-
ods or within an Innovative Technologies glovebox apparatus,14
utilizing glassware that was oven-dried (130 °C) and evacuated
while hot prior to use. Celite (Aldrich) was oven dried (130
°C) for 5 days and then evacuated for 24 h prior to use. Diethyl
ether, pentane, and toluene were dried and deoxygenated by
refluxing for a minimum of 24 h under a flow of dinitrogen, in
the presence of sodium wire. Benzophenone was added to the
solvent/drying agent mixture in order to provide visual con-
firmation (i.e. the observed persistence of the benzophenone
ketyl) that an appropriate level of purification had been
achieved. The solvents used within the glovebox were stored
over activated 3 Å molecular sieves. C6D6 (Aldrich) was
degassed by using three repeated freeze-pump-thaw cycles
and then dried over 3 Å molecular sieves for 24 h prior to use.
CDCl3 (Aldrich) was degassed by using three repeated freeze-
pump-thaw cycles, dried over CaH2 for 7 days, and distilled
in vacuo. iPr2PCl, Ph2PCl, and n-BuLi (1.6 M in hexanes) were
obtained from Aldrich and were used as received, while
[CODRhCl]2 (COD ) 1,5-cyclooctadiene) was obtained from
Strem and dried in vacuo for 24 h prior to use. Indene was
obtained from Aldrich, degassed by using three repeated
freeze-pump-thaw cycles, and distilled under static vacuum
prior to use. Alumina (Aldrich, neutral, 150 mesh, activity
Brockmann II) was degassed and dehydrated in vacuo for 48
h at temperatures between 200 and 300 °C and subsequently
deactivated with 2% deionized water under argon prior to use.
2-(Dimethylamino)indene (1) was prepared by using literature
procedures15 and was dried in vacuo for 24 h prior to use.
Compounds 2a and 3 were also prepared using literature
procedures.4 All NMR data were collected at ambient temper-
ature on a Bruker AC-250 spectrometer at 250.1, 62.9, and
101.3 MHz, for 1H, 13C, and 31P, respectively, with chemical
shifts reported in parts per million downfield of tetramethyl-
NMe2). 13C{1H} NMR (C6D6): δ 148.1 (d, J PC ) 4.8 Hz, sp2 C),
136.5 (sp2 C), 128.8 (sp2 C), 125.6 (d, J PC ) 23.4 Hz, sp2 C),
122.2 (d, J PC ) 16.2 Hz, sp2 C), 119.8 (sp2 C), 118.3 (d, J PC
)
4.3 Hz, sp2 C), 117.8-117.4 (sp2 C’s), 116.9 (sp2 C), 112.8 (sp2
C), 110.3 (sp2 C), 107.8 (sp2 C), 91.4 (sp2 C), 38.1 (d, J PC
29.1 Hz, C1), 31.3 (d, J PC ) 4.3 Hz, N(CH3)2). 31P{1H} NMR
(C6D6): δ 8.1.
)
P r ep a r a tion of 1-(Diisop r op ylp h osp h in o)in d en e (6a ).
In a Schlenk flask containing a magnetic stir bar were added
indene (1.0 mL, 8.6 mmol) and diethyl ether (30 mL). The
reaction flask was sealed with a septum, and the mixture was
cooled to -80 °C. Magnetic stirring was initiated, and a
hexanes solution of n-BuLi (5.4 mL of a 1.6 M solution, 8.6
mmol) was added dropwise over 5 min via syringe, after which
the reaction mixture was warmed to room temperature over
15 h. The clear yellow solution was subsequently cooled to -80
i
°C, and Pr2PCl (1.4 mL, 8.6 mmol) was added via syringe over
3 min. Immediately, a cream-colored precipitate formed from
the yellow-brown reaction mixture. After 20 min, magnetic
stirring was arrested and the reaction mixture warmed to room
temperature over 5 h. The pale yellow solution was then
transferred away from the precipitated solid via cannula
filtration and subsequently dried in vacuo to remove solvent
and any other volatile materials, yielding 6a as a pale yellow
oil (1.85 g, 7.97 mmol, 92%). Since compound 6a slowly
rearranges to 6b on standing, only elemental analysis data
for 6b are provided (vide infra). 1H NMR (C6D6): δ 7.69 (d,
3J HH ) 7.0 Hz, 1H, C4-H or C7-H), 7.30-7.05 (m, 3H, C5-
H, C6-H, and either C7-H or C4-H), 6.71 (m, 1H, C2-H or
C3-H), 6.48 (m, 1H, C3-H or C2-H), 3.71 (m, 1H, C1-H),
1.76 (m, 1H, P(CHMe2)), 1.46 (m, 1H, P(CHMe2)), 1.03-0.98
2
3
(m, 6H, P(CHMe2)), 0.78 (d of d, J PH ) 11.9 Hz, J HH ) 7.0
2
3
Hz, 3H, P(CHMe2)), 0.58 (d of d, J PH ) 14.0 Hz, J HH ) 7.0
Hz, 3H, P(CHMe2)). 13C{1H} NMR (C6D6): δ 147.2 (d, J PC
)
8.6 Hz, C3a or C7a), 144.6 (d, J PC ) 1.9 Hz, C7a or C3a), 137.1
(sp2 C-H), 131.2 (sp2 C-H), 126.8 (sp2 C-H), 125.3 (sp2 C-H),
124.7 (d, J PC ) 7.6 Hz, sp2 C-H), 121.9 (sp2 C-H), 47.0 (d,
1
silane (for H and 13C) or 85% H3PO4 in water (for 31P). In some
cases, slightly fewer than expected independent 13C NMR
resonances were observed, despite prolonged data acquisition
times. Elemental analyses were performed by Desert Analyt-
ics, Tucson, AZ.
1
1J PC ) 28.6 Hz, C1), 23.5 (d, J PC ) 17.6 Hz, P(CHMe2)), 22.6
1
2
(d, J PC ) 18.6 Hz, P(CHMe2)), 21.6 (d, J PC ) 4.8 Hz,
2
2
P(CHMe2)), 21.3 (d, J PC ) 5.3 Hz, P(CHMe2)), 20.9 (d, J PC
)
12.9 Hz, P(CHMe2)), 20.7 (d, J PC ) 9.5 Hz, P(CHMe2)). 31P-
2
P r ep a r a tion of 1-(Dip h en ylp h osp h in o)-2-(d im eth yl-
{1H} NMR (C6D6): δ 17.3.
a m in o)in d en e (2c). Compound 2c was prepared on the basis
of the literature preparation of 2a .4 In
a Schlenk flask
P r ep a r a tion of 3-(Diisop r op ylp h osp h in o)in d en e (6b).
Within the glovebox, a freshly prepared solution of 6a (1.99 g,
8.60 mmol) in diethyl ether (30 mL) was passed down an
alumina column (2 cm × 4 cm). The eluted yellow solution was
dried in vacuo to remove the solvent and any other volatile
materials, yielding 6b as a yellow oil (1.52 g, 6.53 mmol, 76%).
Anal. Calcd for C15H21P: C, 77.56; H, 9.11. Found: C, 77.54;
containing a magnetic stir bar were added 2-(dimethylamino)-
indene (0.66 g, 4.17 mmol) and THF (20 mL). The flask was
then sealed with a septum and cooled to -80 °C. Magnetic
stirring was initiated, and a hexanes solution of n-BuLi (2.6
mL of a 1.6 M solution, 4.2 mmol) was added dropwise over 3
min via syringe, after which the reaction mixture was warmed
to room temperature over 3 h. Subsequently, the reaction flask
was again cooled to -80 °C and chlorodiphenylphosphine (0.75
mL, 4.17 mmol) was added via syringe over 2 min. The
resulting clear tan solution was warmed to room temperature
and was stirred for 15 h. The THF and other volatile materials
were then removed in vacuo, and the residue was washed with
diethyl ether (15 mL) and dried in vacuo, leaving a cream-
colored solid. Treatment of this solid with toluene (15 mL)
1
3
H, 9.08. H NMR (C6D6): δ 7.82 (d, J HH ) 7.6 Hz, 1H, C7-H
or C4-H), 7.29-7.07 (m, 3H; C5-H, C6-H, and either C4-H
or C7-H), 6.42 (m, 1H, C2-H), 3.10 (s, 2H, CH2), 2.01 (d of
2
3
septets, J PH ) 2.1 Hz, J HH ) 6.9 Hz, 2H, P(CHMe2)2), 1.08
2
3
(d of d, J PH ) 14.7 Hz, J HH ) 7.0 Hz, 6H, P(CHMeaMeb)2),
0.99 (d of d, 2J PH ) 11.9 Hz, 3J HH ) 7.0 Hz, 6H, P(CHMeaMeb)2).
13C{1H} NMR (C6D6): δ 148.7 (d, J PC ) 18.6 Hz, quaternary),
144.6 (d, J PC ) 3.8 Hz, quaternary), 141.8 (d, J PC ) 5.7 Hz,
sp2 C-H), 140.5 (d, J PC ) 23.4 Hz, quaternary), 126.9 (sp2
C-H), 125.5 (sp2 C-H), 124.3 (sp2 C-H), 122.3 (d, J PC ) 6.7
(14) Szafran, Z.; Pike, R. M.; Singh, M. M. Microscale Inorganic
Chemistry; Wiley: Toronto, 1991.
(15) (a) Klosin, J .; Kruper, W. J ., J r.; Nickias, P. N.; Roof, G. R.; De
Waele, P.; Abboud, K. A. Organometallics 2001, 20, 2663. (b) Edlund,
U.; Bergson, G. Acta Chem. Scand. 1971, 25, 3625.
Hz, sp2 C-H), 40.3 (d, J PC ) 3.8 Hz, CH2), 23.3 (d, J PC ) 11
3
Hz, P(CHMe2)), 21.0 (d, J PC ) 17.6 Hz, P(CHMe2)), 19.9 (d,
J PC ) 10.0 Hz, P(CHMe2)). 31P{1H} NMR (C6D6): δ -10.2.

Rh(I) Chemistry of Donor-Functionalized Indenes
Organometallics, Vol. 22, No. 25, 2003 5191
P r epar ation of [Rh Cl(η4-1,5-cyclooctadien e)(K1-3-iP r 2P -
in d en e)] (7). In a glass vial charged with a magnetic stir bar,
6b (0.038 g, 0.16 mmol) was dissolved in toluene (3 mL). In a
separate glass vial, [CODRhCl]2 (0.040 g, 0.08 mmol) was
slurried in toluene (2 mL) and transferred via Pasteur pipet
to the stirred solution of 6b, resulting in a clear yellow-orange
solution. The reaction vial was then sealed with a PTFE-lined
cap. After 10 min, a yellow solid formed. The reaction mixture
was then stirred for an additional 1.5 h, after which the
supernatant was transferred away from the precipitated yellow
solid via Pasteur pipet. By slightly concentrating the super-
natant in vacuo, a further yellow solid precipitated, which was
isolated and combined with the original solid fraction. The
combined solids were then dried in vacuo to remove the
remaining solvent and any other volatile materials, yielding
7 (0.062 g, 0.13 mmol, 79%). Anal. Calcd for C23H33PClRh: C,
After 2 h, a slurry of [CODRhCl]2 (0.040 g, 0.08 mmol) in
diethyl ether (2 mL) was added to the reaction mixture via
Pasteur pipet, whereupon the solution turned dark orange
with the formation of a precipitate. After it was stirred for 16
h, the reaction mixture was filtered through Celite. 31P NMR
analysis of the clear brown-green filtrate revealed the presence
of a single new phosphorus-containing product. Solvent and
other volatile materials were then removed in vacuo, the
resulting dark green greasy solid was washed once with
pentane (1 mL), and the product (9) was dried in vacuo (0.064
g, 0.14 mmol, 88%). Anal. Calcd for C23H32PRh: C, 62.45; H,
7.29. Found: C, 62.12; H, 7.27. 1H NMR (C6D6): δ 7.45 (d, 3J HH
3
) 7.6 Hz, 1H, C4-H or C7-H), 7.28 (d, J HH ) 7.6 Hz, 1H,
C7-H or C4-H), 7.08-6.96 (m, 2H, C5-H and C6-H), 5.77
(m, 1H, C2-H or C3-H), 4.77 (d, J ) 2.4 Hz, 1H, C3-H or
C2-H), 3.98 (m, 2H, vinyl CH's), 3.75 (m, 2H, vinyl CH’s), 2.23
(m, 1H, P(CHMe2)), 2.12-1.27 (m, 12H, P(CHMeMe) and
(CH2CH2CHCH)2), 1.15 (d of d, 3J HH ) 7.0 Hz, 3J PH ) 12.8 Hz,
1
57.69; H, 6.95. Found: C, 57.45; H, 7.00. H NMR (C6D6): δ
3
8.34 (d, J HH ) 7.6 Hz, 1H, C7-H or C4-H), 7.27-7.08 (m,
3
3
3H, C5-H, C6-H, and either C4-H or C7-H), 6.16 (m, 1H,
3H, P(CHMeMe)), 1.03 (d of d, J HH ) 7.3 Hz, J PH ) 13.1 Hz,
3 3
C2-H), 5.77 (s, 2H, vinyl-CH’s), 3.46 (s, 2H, vinyl-CH’s), 2.96
3H, P(CHMeMe)), 0.90 (d of d, J HH ) 7.0 Hz, J PH ) 10.1 Hz,
3H, P(CHMeMe)). 13C{1H} NMR (C6D6): δ 123.6 (sp2 C-H),
122.2 (sp2 C-H), 121.1 (sp2 C-H), 120.3 (d, J ) 5.7 Hz, sp2
C-H), 96.3 (t, J ) 4.3 Hz, sp2 C-H), 76.5 (d, J ) 4.3 Hz, sp2
3
(s, 2H, C1-H’s), 2.58 (m, 2H, P(CHMeaMeb)2), 2.10 (d, J HH
)
7.6 Hz, 2H, CH2CH2), 1.56-1.68 (m, 4H, CH2CH2), 1.49 (d of
d, J PH ) 15.8 Hz, J HH ) 7.0 Hz, 6H, P(CHMeaMeb)2), 1.34
3
3
3
3
(m, 2H, CH2CH2), 1.06 (d of d, J PH ) 13.7 Hz, J HH ) 6.7 Hz,
6H, P(CHMeaMeb)2). 13C{1H} NMR (C6D6): δ 142.9 (sp2 C-H),
126.3 (sp2 C-H), 125.9 (sp2 C-H), 125.2 (sp2 C-H), 124.2 (sp2
C-H), 103.9 (d of d, 1J RhC ) 12.4 Hz, 2J PC ) 7.2 Hz, COD vinyl
C-H), 70.6 (d, J RhC ) 13.8 Hz, vinyl CH's), 70.0 (d of d, J PC )
4.3 Hz, J RhC ) 13.8 Hz, vinyl CH’s), 32.2 ((CH2CH2CHCH)2),
1
31.5 ((CH2CH2CHCH)2), 25.9 (d, J PC ) 16.2 Hz, P(CHMe2)),
1
2
23.0 (d, J PC ) 17.6 Hz, P(CHMe2)), 22.9 (d, J PC ) 11.4 Hz,
1
3
2
2
C’s), 71.0 (d, J RhC ) 13.3 Hz, COD vinyl C’s), 40.2 (d, J PC
6.7 Hz, C1), 33.5 (d, J PC ) 2.9 Hz, P(CHMe2)), 24.5 (d, J PC
)
)
P(CHMe2)), 21.1 (d, J PC ) 9.5 Hz, P(CHMe2)), 20.9 (d, J PC )
2
11.4 Hz, P(CHMe2)), 19.5 (d, J PC ) 7.2 Hz, P(CHMe2)). 31P-
{1H} NMR (C6D6): δ -11.8.
23.8 Hz, P(CHMe2)), 21.1 (d, J PC ) 3.8 Hz, P(CHMe2)), 29.1
(s, COD CH2), 19.5 (s, COD CH2). 31P{1H} NMR (C6D6): δ 25.7
F or m a tion of 10. In a Schlenk flask equipped with a
magnetic stir bar, 6b (0.12 g, 0.54 mmol) was dissolved in
diethyl ether (10 mL) within the glovebox. The reaction flask
was sealed with a septum and transferred to the Schlenk line.
The flask was then cooled to 0 °C, and magnetic stirring was
initiated. A hexanes solution of n-BuLi (0.86 mL of a 1.6 M
solution, 1.4 mmol) was subsequently added to the flask over
2 min via syringe, and the yellow solution was then stirred
for 2 h as it warmed to room temperature. A 31P NMR
spectrum taken of an aliquot of this yellow solution confirmed
the clean formation of 6-Li. The reaction flask was then taken
back into the glovebox, and a slurry of [CODRhCl]2 (0.13 g,
0.26 mmol) in toluene (4 mL) was added via Pasteur pipet.
Immediately, the reaction mixture turned dark red-brown and
a lightly colored precipitate formed. After 1 h, 31P NMR
analysis of the reaction solution revealed the formation of 9
(δ -11.8) as the major product. The reaction mixture was then
concentrated in vacuo and filtered through Celite into a glass
vial. The vial was then sealed with a PFTE-lined cap and
stored at -30 °C. Initially, no crystalline material was
produced. However, after 3 months a minute quantity of red
crystals was isolated by transferring the supernatant away
via Pasteur pipet into a separate glass vial. Single-crystal
X-ray analysis of the isolated crystals revealed their identity
to be 10. A subsequent 31P NMR analysis of the supernatant
from which the crystals had grown revealed a sharp singlet
at δ -11.8 (attributable to 9) but also many new rhodium-
coupled products in the range δ 75.9-48.9. Satisfactory NMR
data for the isolated crystals of 10 could not be obtained, and
no further material was isolated from this reaction mixture
in pure form.
1
(d, J RhP ) 152 Hz).
P r ep a r a tion of [Rh (η4-1,5-cycloocta d ien e)(η5-2-Me2N-
C9H6)] (8). In a Schlenk flask containing a magnetic stir bar
were added 1 (0.11 g, 0.67 mmol) and diethyl ether (10 mL),
producing a light tan solution. The flask was then sealed with
a septum and cooled to 0 °C. A hexanes solution of n-BuLi
(0.42 mL of a 1.6 M solution, 0.67 mmol) was added to the
stirred solution over 5 min. The reaction flask was then
warmed to room temperature over 2 h, during which time a
white solid precipitated. The flask was transferred to the
glovebox, and a slurry of [CODRhCl]2 (0.17 g, 0.34 mmol) in
diethyl ether (4 mL) was added via Pasteur pipet. Immediately,
a dark brown-red solution formed, along with what appeared
to be a fresh white precipitate. The reaction mixture was
stirred for 1 h followed by filtration through Celite. Fine brown
fibers of 7 readily precipitated from the solution, which were
isolated by transferring the supernatant away with a Pasteur
pipet and drying in vacuo to remove any remaining solvent
and other volatile materials (0.13 g, 0.36 mmol, 53%). Anal.
Calcd for C19H24NRh: C, 61.79; H, 6.55; N, 3.79, found: C,
60.43; H, 6.50; N, 3.61. Repeat analyses consistently yielded
1
low % C values. H NMR (CDCl3): δ 7.30-7.21 (m, 4H, C4-
H, C5-H, C6-H, and C7-H), 5.05 (s, 2H, C1-H and C3-H),
4.29 (s, 4H, vinyl CH’s), 2.97 (s, 6H, N(CH3)2), 2.18-1.97 (m,
8H, (CH2CH2CHCH)2). 13C{1H} NMR (CDCl3): δ 121.6 (C4 and
C7 or C5 and C6), 118.0 (C5 and C6 or C4 and C7), 67.7 (d,
1J RhC ) 13.3 Hz, vinyl C’s), 64.8 (d, J RhC ) 4.8 Hz, C1 and C3),
42.7 (N(CH3)2), 31.8 ((CH2CH2CHCH)2).
P r ep a r a tion of [Rh (η4-1,5-cycloocta d ien e)(η5-1-iP r 2P -
C9H6)] (9). Within the glovebox, a hexanes solution of n-BuLi
(0.10 mL of a 1.6 M solution, 0.16 mmol) was added to a stirred
solution of 6b (0.037 g, 0.16 mmol) in diethyl ether (2 mL),
and the vial was sealed with a PFTE-lined cap. A 31P NMR
spectrum taken of this yellow reaction solution revealed the
presence of 6-Li as the only phosphorus-containing product.16
Isom er iza tion of 1-(Diisop r op ylp h osp h in o)-2-(d im eth -
yla m in o)in d en e (2a ). Within the glovebox, a 0.02 g sample
of 2a was dissolved in C6D6 (2 mL) in a glass vial equipped
with a magnetic stir bar. The initial 31P NMR spectrum of this
solution revealed only one signal at 19.6 ppm. To this solution
was added alumina (2 g), and the vial was subsequently sealed
with a PTFE-lined cap. After the mixture was stirred for 2 h,
(16) We have found lithium salts of phosphinoindenes to be rather
unstable in the solid state. As such, the preparation of 6-Li is carried
out in situ by treating a solution of 6b with n-BuLi. We attribute the
single phosphorus resonance in the 31P NMR spectrum (δ -8.9) of the
resulting solution to 6-Li.
a
31P NMR spectrum was obtained of the resulting yellow
solution, which revealed two resonances at chemical shifts of
19.6 ppm (2a ) and -2.9 ppm (tentatively assigned as 2b) in

5192 Organometallics, Vol. 22, No. 25, 2003
Cipot et al.
an approximate ratio of 3:1. The mixture was stirred for 2
weeks with periodic monitoring by using 31P NMR spectros-
copy; no further changes in the peak ratios were observed.
Isom er iza tion of 1-(Dip h en ylp h osp h in o)-2-(d im eth yl-
a m in o)in d en e (2c). Using a protocol analogous to that
described for the isomerization of 2a , a freshly prepared
sample of 2c (0.02 g) dissolved in C6D6 (2 mL) was stirred over
alumina (2 g). After 2 h, a 31P NMR spectrum obtained from
an aliquot of the reaction mixture revealed two resonances at
chemical shifts of 8.1 ppm (2c) and -24.8 ppm (2d ) in an
approximate ratio of 1:3. The mixture was stirred for 72 h with
periodic monitoring by using 31P NMR spectroscopy; no further
reduction, and absorption correction were those supplied by
Bruker. Structural refinement was carried out by using full-
matrix least-squares methods on F2 with anisotropic thermal
parameters for all non-hydrogen atoms. Hydrogen atoms
were added at calculated positions and refined using a riding
model. Complete details are provided in the Supporting
Information.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada, the
Canada Foundation for Innovation, the Nova Scotia
Research and Innovation Trust Fund, and Dalhousie
University for financial support. We also thank Mr.
J uergen Mueller (Dalhousie) for the preparation of
custom Schlenk glassware and Dr. Michael Lumsden
(Atlantic Region Magnetic Resonance Center, Dalhou-
sie) for assistance in the acquisition of NMR data.
1
changes in the peak ratios were observed. H NMR (C6D6) for
2d : δ 7.74-7.71 (m, 2H, Ar H’s), 7.21-6.91 (m, 10H, Ar H’s),
6.87-6.83 (m, 2H, Ar H’s), 3.09 (s, 2H, CH2), 2.71 (s, 6H,
NMe2).
X-r a y Cr yst a llogr a p h y. Single-crystal samples of 2d
and 3‚C6H6 were obtained from hexanes and benzene, respec-
tively, by slow solvent evaporation; crystalline samples of 7
and 10‚C7H8 were grown from toluene and toluene/diethyl
ether (1:1), respectively, at -30 °C. X-ray crystallographic data
for 2d , 3‚C6H6, 7, and 10‚C7H8 were collected on a Bruker
PLATFORM/SMART 1000 CCD instrument at 193(2) K, using
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å).
Programs for diffractometer operation, data collection, data
Su ppor tin g In for m ation Available: Tables giving single-
crystal X-ray diffraction data for 2d , 3‚C6H6, 7, and 10‚C7H8;
these data are also available as CIF files. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM0340589